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Old 24th September 2002, 02:31 AM   #1
Gabster is offline Gabster  Canada
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Default Blue glowing tube

I've not been able to find it, but not so long ago, I saw on this forum a tube amplifier with blue glowing tubes. What kind of tubes are they? I've read somewhere it has to do with mercury gas but I don't really know...

Anyway, the point is that I want to build a tube headphone amplifier and I believe it would be very cool if it could use that kind of tubes. Is there good designs using these (diy-ready)?

thanks a lot,
Gabriel
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Old 24th September 2002, 04:05 AM   #2
Colt45 is offline Colt45  Serbia
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They are no good for this kind of stuff.. overkill, plus a PITA to implement.

You need to warm them up before you turn on the HV, or they croak.

Plus a headphone amp just doesnt need that much power..

I've got some 866's, they're good for 250mA @ 10Kv or something crazy like that, IIRC.

The UV might be bad for your eyes too, or does the glass stop it?

I had a better response typed up, but IE screwed up

heres a pic of a 866 (my poor camera doesnt do it justice.. looks much better in real life).
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Old 24th September 2002, 12:12 PM   #3
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Default BLUE TUBES

Fellows,

Those huge valves aren't the only ones.
Way back then,in the early days of radio you had quite a few of these cute blue tubes.
Well,in Europe at least.
With the most lovely shaped bulbs to boot.
IMO,but check it out with the HAM folks, it served the purpose of tempering the influence of incoming light.
Say much the same way you will find some graphite coating on the inside of some older coke bottle shape 6L6's,6Y6 to name but a few.
And I agree it looks cool.
I recall former Tesla EL34's whitch we're done with the same kind of blue glass.
The Japanese audio scene was the major buyer of these.

Cheers,
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Old 24th September 2002, 12:39 PM   #4
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I have never seen one myself, but I understand that mercury
rectifiers once was the only way to rectify high currents/voltages.
I have heard people referring to the strong blue glow from the
inner of certain electric railway engines, eg. the sewdish Ra
and Rb series back in the late 50s/early 60s, before high
power thyristors were available. In this case we are not
talking W or kW, but MW! These were not small valves/tubes
but tall glass columns, I am told.

Sorry for posting off-topic for the forum, but it seemed
a bit on-topic for the thread.
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Old 24th September 2002, 01:25 PM   #5
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Default 250ma @ 10kV

That much ?

They must be great for Electrostatic Loudspekers !



grtz


Simon
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Old 24th September 2002, 01:54 PM   #6
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Hello,

There is very simple way to make every tube glowing blue.
There is no any sound difference however.
It just looks very unusuall and cool.

You simply install high-efficiency Blue LED below tube !
I tried, and it looks very different than the rest normal glowing
tubes.


Best regards,
Kristijan Kljucaric
http://web.vip.hr/pcb-design.vip
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Old 24th September 2002, 02:56 PM   #7
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Or just use some nice Blue tubes like these Arcturus made in the 30's. The 127's can make for nice sounding line stages but many are hopelessly microphonic....

Dave

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Old 24th September 2002, 06:43 PM   #8
Ken L is offline Ken L  United States
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Default Don't know what you saw before

but I've got a couple of pairs of 872's that are mercury vapor types that burn blue. They will be used for rectification on a 304TL amp - you're looking at about 1500 volts here -

The 304tl amp will be SET but due to the higher voltage will put out in the neighborhood of 45 watts.

The most widely known of the 304tl's is probably from Moth Audio.

http://www.mothaudio.com/ts-m304tl.html

I've been assembling parts for a Jim Dowdy design for almost a year - interstage transformer due in soon which only leaves the Plitron output and I'll have all the main parts



Ken L
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Old 24th September 2002, 06:55 PM   #9
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I used (2) 816 Mercury Vapor 1/2 wave rectifier tubes in the power supply I built for my new homemade tube preamp project. They have a nice blue glow but it doesn't show up well in the photo...

Dave

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Old 24th September 2002, 07:17 PM   #10
Ken L is offline Ken L  United States
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Thumbs up Nicely done

Good looking preamp.

Is it sounding like you want?

I've recently finished (?) a Dowdy designed Preamp - debugging it - having problems getting the AC hum out -

Real Life intrudes in the form of work (some), and home renovation (major), I left it with Jim a few weeks ago -because we're moving everything out of the house we can due to the renovation.

What part of Va are you located in?

Did I meet you in Knoxville a couple of weeks ago at Phil's??

Ken L
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